Spring toggle mechanism



Feb. 7, i950 STIMSON 2,496,896

SPRING TOGGLE MECHANISM 2 Sheets-Sheet 1 Original Filed Oct. 1.9, 1946 in v 1 i w 411W r" I 4 2 67 Inventor:

Allen (3. Stimson,

His Attorney.

Feb. 7, 1956 A. G. STIMSON SPRING TOGGLE MECHANISM 2 Sheets-Sheet 2 Original Filed Oct. 19, 1946 Inventor-z Allen (3. Stimson,

His Attorney.

ing correct 7 H There are features of the meter and calculator 45 Patented Feb. 7, 1950 SPRING TOGGLE MECHANISM Allen G. Stimson, Lynnfield, Mass., assignor to General Electric Company, a corporation of New York Original application October 19, 1946, Serial No. 704,352. Divided and this application August 29, 1947, Serial No. 771,349

This is a division of my application Serial No.

704,352, filed October 19 1946, nowPatent No. r 2,471,171 relating to a combined exposure meter and calculator, and this divisional application re.-

lates to a spring toggle mechanismemployed in Q the device of the parent application, and its object is to provide a spring togglemechanism particularly suited to the confined space available in such devices. To this end I employ a toggle spring which has one end double-backed on itself, whereby the distance between the points of attachment of the spring is reduced, and the r I toggle leverage action thereof is increased incomparison to the useful length of the spring ,employed. la

The features of my invention which are novel and patentable will be pointed outin the claims appended hereto. For a better understanding of "my invention, reference is made inthe following description to the accompanymg drawing in which Fig. 1 represents a face .view ofmy ex posure meter and calculator; Fig. 2 is a similar view with the calculator removedand exposing a portion of the driving mechanism between the calculator and meter scale changing mechanism;

on either side of index I3. This arrangement is intended to expose only that range of light Fig. 3 is a face view of the meter with the cover section of its casingremovedandwith the scale ,and sensitivity changing mechanism in position .for maximum sensitivity and low'light values; Fig. 4 is a similar view to that of Fig. 3, except with the parts in position for minimum sensitivity and high light values; Fig. 5 is a schematic axially exploded View of the meter scale changing mechanism and associated parts Fig. 6 isa side view of the complete instrument; Fig.7 is a Qsectional view through the calculator; and Fig.

8 is an interior view of the backjsectioniof the casing with part of the instrument and light cell .broken away and showing the rear, transparent .closure window through which the lightcell. is j'exposed.

The apparatus to be described comprises a combination light meter and calculator for "obtain-- photographic exposure information.

and their combination which are believed to be novel and patentable. v

Fig. 1 is a front view and Fig. 6 is a side view of the external appearanceof the apparatus. .The

over-all width of the instrument as built is slightly less than 2 inches audits total thickness is slightly greater than one inch. 'Itsjshape is approximately that of a pocket watch. It may,

therefore, be carried in a vest pocket without inconvenience. The calculator .of the instrument,

the main parts of which comprise a stationary masking plate I, a movable outer calculator ring 1 Claim. (01. 749'7) dicated at 9. t

2 2 and a movable inner calculator ring 3' (Figs. 1, 5 and 7) is mounted on the front of the instrument and removably held in place by screws 4.

f'Ihese calculator parts have an elongated opening 5 extending through and across their central portions through which the light meter pointer 6 and its interchangeable scales I and 8 may be viewed for the purpose of light value measurements. The stationary masking, plate I of'the 'calculator also contains an opening at 9 to expose the selected number on a film speedscale I0 reading from .2 to 1600 and marked about one-half of the periphery of the inner adjustable calculator ring 3. A lens diaphragm j-stop scale 8 I reading from 1 to 128 is marked on a remaining sector of disk 3. The outer adjustable calculator ring has a light value scale I2 marked about slightly less than half of its periphery reading from .05 to 2000. This scale cooperates with the film speed indication exposed in window 9 in the use of the calculator, and the mask- 'ing plate has a stationary index tab I3 opposite jwindow 9 indicating on scale I2. The plate I has sector rim extensions which mask the upper part of scale I2 except over a selected limited range values which are significant and corresponds to the brightness range which can be usefully refwhich marks the'allowable brightness range for color film for which the film speed would be in- .The outer ring 2 also carries a time scale I4 :about the rim opposite to scale I2 graduated from /32oo to seconds, which scale cooperates with the stop scale II to indicate the combinations of shutter speed and relative apertures of the lens that may be used for a given I film speed and light value.

v The outer ring 2 contains a short upstanding pin I5 near the /2-second graduation and ring 3 contains two such pins I6 and I1 near the 2 and 16 graduations thereon. These pins are used to assist in turning the rings and to limit their movements to the useful ranges by acting as stops against the lower edges of the extended sectors of masking plate I at points I8 and I9. These extended sectors have a rim section Ia bent toward thebeveled ring 2 and retain both the outer and inner rings, 2 and 3 in place as best shown in Figs. 5 and 6. Masking plate I,is

riveted to a calculator base plate 20 which has "hub, sectors 20a (seeFig. 5) on which the inner periphery of inner ring 3 rides. Base plate 20 contains a recess in its upper surface below the window opening in which a spring pressed detent is provided and pinned toplatef2fl for holding the ring 3 from turning except when the detent is released. The spring portion 2|, detent portion 22, and releasing handle 23 of this detent are made in one piece (see Fig. 5). Thedetenttportion 22 engages with teeth out into the inner periphery of ring 3 over the range of movement of the latter past the detent. The handle portion 23 of the spring detent unit is bent down and out through an opening "cut in the bottom of base plate where it is accessible to be pressed radially inwardly by the thumb or finger of the operator. Such pressure pushes the detent;22 out of a depression in ring 3 and allows the latter to :be turned. The tooth spacing in ring .3 corre- .sponds to the smaller graduation markspac'ing of the .film speed scales on ring -3 such that move- .ment of ring 3 one .detent notch moves it .onefilm :speedscale division. 'The outer ring 2 has upper and lower circularrecesses cutinits inner periphery as-shown in Fig. 7; the upper recess forms a seat :for the inner ring .3 .and the lower recess rides on the outer periphery of base plate .20. The masking ,plate I and base plate 20 areriveted together with the rings 2 and 3 between them. Theouter ring 2 has aknur-led outer periphery to-iacilitate easy turning. As thus :far described, the calculator may be removed from the instru- :mentand used as such with any light meter, .and another calculator mechanicallySimilar but with different scale markings substituted in its ,place. However, .-for use on the light .meter instrument i to be'described, the outer ring 2 has a-.pin.24 pro- .jecting from .its back side .for cooperation with .a .mechanism (for changing the light measurement .range of the meter as will be explained .in connection with Fig. :5. This pin .24- rides in a circular groove :25 cut .in the upper wall 29 of the meter (see Fig. 2) and engages with one .or the other of .arms 26 and :21 .of the mechanism just referred to .for the purpose of operating the sensitivity and scale changing mechanism of the lightmeter by turning of ring 2 of the calculator andrequiring the proper lightmeasurementrange to-be-used for calculator settings when usinghigh and low light values.

The slot at 28, Fig. 2, in the front wall .of the meter-casing is toaccommodate the-detenthandle 23, and'a-llow the calculator unit to be mounted closely to such front wall, thus keeping the total thickness within desired limits. The .front wall .of theimeter casingcontains a transparent window 3D in line with the window openings in the calculator. Theifront wall29 .is recessed at 3| to about the .depthof groove .25 to accommodate a rotary member 32 with which the arms 26 .and 21 are integral. The member 32 .has .a bearing through the front wall 290f themeter casing,-and .its rear side, within the .meter casing, has driving -arms 33 and 34 with their extremities .bent to the rear. Themember32 may-be .made lip-of apair ofz-fiat metal parts resting against the vfront and rear sides of the wall 19 and riveted together through acii'culariopening 35 in the wall so that .it is .rotativelymounted in the wall for the .pur- .pose of transmitting limited rotary motion therethrough for the purpose of changing the .sensi- .tivity and scale -of the light measuring instrument by turning the lightscale of the calculator.

.It is .to be observed that in Fig. 5 certain parts are .shown greatly extended in the axial direction whereas actually the total length of the device '4 32, 33, 34 is less than the diameter of portion 32 thereof.

The meter casing comprises the front cover wall part #29 already mentioned anda rear portion 35. These parts have integral side walls which extend toward each other and resemble a pair of generally rectangular shallow cups which when placed mouth to .mouth form the meter casing. These parts are held together by a pair of screws 31 "which are'threadedinto holes 3111. in the rear part of the casing (see Figs. 2 and 3). When the screws are removed, the casing may be opened. Fig. 2 shows the :casing closed, and in Figs. 3 and 4 the front section has been removed. The rear wall of the casing contains a large glass window through which a flat light cell 38 placed in the bottom of the casing may be exposed to lightior-the purpose of taking a brightness measurement. Fig. '8 shows .an interior view of the lower casing section containing the window 39 and portions of the light cell 38. The window has closely spaced louvers .at right angles to each other, indicatedbycross-sectional lines in'Fig. 8, for the purpose ofrequiring the light which enters through the window to do so from a direction essentially perpendicular to the face of the window. This facilitates correct brightness measurements from selected directions without the use of a projecting directional hood. Such a window maybe made up .to two 0.044 inch thicknesses or .Louverplas .sold by Ivan T. Johnson Company. The louvers are spaced 0.033 inch apart and are approximately four .mils thick and perpendicular to the surface of the transparent plastic in which contained. The louvers in one sheet or thickness of the material run in one direction and those in the other sheet at right angles to such direction to form the directional light window used.

The lightcell .38 is placed directly back of and .fiat against the window with its light sensitive 'surface exposed thereto. The cell is held in .placein the-bottom of the casing by clips 40 and forms a base for an electrical measuring instrumentpartiallyrshown in Fig. 4 having a stationary permanent magnet field 40' and a moving armature coil 4.| pivoted about a magnetic core 42 contained in agap in the permanent magnet circuit. In order not to shunt flux from the permanent magnetno magnetic material is used "in the cell structure. The cell 38 and magnet 40' .are ,placed flatly against each other back to back. "The axis of rotation of the armature is perpendicular to the light cell. To allow room for the lower pivot .and lead-in spiral of the armature'b'elow the level of the permanent magnet, an opening 43 therefor is provided in the .cell and also in the inner section of window '39. The lower extremity of the armature coil and its pivot and spiral .are contained in such opening. This construction is for the purpose of keeping the complete device as thin as practicable. The instrument pivots are of the internal type and turn injewels in'the ends of the core 42. 'The core is secured in place by a strap 44 (see .Figs.2 and 5) fastened to its top end and extendin'g radially therefrom to a bridging plate BI.

A zero adjustment for the instrument comprises-a ring 46 '(Fig. 4) fitting a counterbore in the inner periphery of the circular opening 43 in the photocell. 'The outer end of the lower spiral for the instrument is secured to ring 46 and the ring is:rotatively*adjustable in such opening. For thisypurposea tab 41 rises from the ring. Such tab hasa vertical slot therein .-for reception :of an eccentric pin projecting from the end of a screw 48 extending through and rotatable in the side wall of the casing. The eccentric pin extends into the slot in tab 41 and when the screw is rotated, the zero position of the instrument pointer is adjusted. The lower lead-in spiral of the instrument is connected directly to one side of the light cell.

The measuring instrument is bolted to the light cell base by two bolts 49 and 50. One of these bolts 50 is insulated from the magnet structure and rear of the light cell and is also used as the otherterminal between the light cell and upper lead-in spiral of the instrument. The inner thickness of the louvered window 39 has openings 5| and 52 opposite these bolts to make room for their heads on the window side of the cell and for making the electrical connection from the cell to the bolt 50.

In order to measure light values with acceptable accuracy over the entire range likely to be met with in practice, I provide two ranges of sensitivity for the electrical measuring instrument and two light value scales therefor, together with means for simultaneously changing from one condition of sensitivity and the scale corresponding thereto to the other condition of sensitivity and its corresponding scale. For the higher light value measurements, I connect a resistance 53 in shunt to the armature coil 4|, and for low light value measurements this shunt is opened by a switch 54 as represented in the circuit diagram portion of Fig. 5. The switch 54 is shown in the open position and is closed by sliding the movable switch contact 54 upwards. Contact 54 may be slid up and down by or with a crank arm 55 which turns with a shaft 56 extending from the interior to the exterior of the casing where it is provided with an operating tab 51 adapted to be moved between its two operating positions by the thumb of the user. This same crank arm 55, 56, 51 may be used to operate the scale chang-'- ing mechanisms.

Two scales 1 and 8 are provided, one, 1, shown in Figs. 1, 2, and 3, reading from to 20 for low values of light and the other, 8, shown in Fig. 4, reading from 0 to 2000 for high values of light. The shunt resistance 53 is of such a value that the value 20 on both scales corresponds to the same light value and with a corresponding change in instrument sensitivity. I

These scales are marked side by side on the slidable scale plate 58 in about the positions indicated in Fig. by reference characters 1 and 8. The low light value scale 1 is exposed through the window openings 5, when scale plate 58. is up and switch 54 down and open, and the high light value scale 8 is exposed through the window openings 5 when the plate 58 is down and switch 54 up and closed. Scale plate 58 slides vertically on stationary guide pins 59 contained in vertical slots in such plate. These rods are supported between and also space stationary supporting plates 60 and 6|, the plate 6| comprising the bridge plate of the measuring instrument previously mentioned. Plate 60 contains a window opening 5a in line with openings 5 but somewhat narrower in width. The sliding scale plate 58 is moved by means of a lever 62 pivoted to plate 6| at 63 and connected to crank arm 55 by the extension at 64. The shift of the scale plate from one position to the other is accompanied by a mild toggle snap action by reason of a spring 65 subject to compression between the effective operating end of lever 62 and a stationary point 66 positioned within the angle of throw of such lever end and more remote from the pivot point 63 of such lever than the point of attachment of the spring to such lever. With such arrangement the spring is under greatest compression when the lever 62 is near the midpoint of its extreme positions and hence snaps the lever from the dead-center position of the toggle to the ex treme operating positions of the lever determined by the length of the slots in scale plate 56.

The spring 65 is unique in construction by rea-' son of having one end doubled back towards its center and fastened at point 66 to the stationary supporting structure. This makes its effective useful length about twice as long as the distance between its points of support. This provides for greater uniformity of spring tension over the throw of the toggle than would be possible with a compression spring positioned entirely between the points of support. Also, at the same time the spring does not take up as much room as a spring of the same effective length supported at its Opposite ends. The fork in the end of crank arm 55 engages fairly loosely with the extension 64 of the scale plate lever and with the eye in the upper end of switch member 54, so that the mechanism operates smoothly without binding and the toggle action gives the desirable amount of snap action and assures complete movements. The action is such as alternately to exactly center the two scales on plate 58 in the window openings provided. The central portion of the operating lever 62 also cooperates with the driving arms 33 and 34 of the calculator mechanism 32 on which the arms 26 and 21 are mounted and previously mentioned in connection with Fig. 2.

The electrical sensitivity and the scale changing mechanism of the light meter may be operated by the turning of calculator ring 2 through the lost-motion operating mechanism compris ing pin 24 and mechanism 32 with its driving arms 26, 21, 33, and 34 operating on lever 62, as well as by means of the crank arm 55 and operating tab 51. The purpose of this arrangement is for the convenience of the user and for promoting correct and most accurate use of the combined instrument as will appear from the following.

The mechanism as represented in Fig. 5 is ad'- justed for low values of light. That is, the electrical instrument is connected without the shunt for high sensitivity, the low value light scale 1 is exposed, and the calculator ring 2 is in a position to bring the low light valuerange of its light scale I2 opposite pointer index l3. Assume, for

instance, that the apparatus has just been used for measuring a light value corresponding to the .position of pointer 6 on scale 1 of 5, and that the calculator was set accordingly with the value 5 on scale I2 of ring 2 opposite index l3. Assume now that the light value increases to a value 50. Pointer 6 will move off the upper end of scale 1. The user may simply turn the ring 2 clockwise until pin 24 engages arm '26 and then slightly farther to change --the sensitivity and I light scales of the meter through the device 32 without touching tab 51. This change will occur at about the point where 50- on scale 12 passes 1 index I 3. As the change occurs, arm 26 moves counterclockwise out. of the path of movement of pin 24 and arm 21 moves into such path behind or to the right of pin 24.

In the same way going from high light value and corresponding setting of the calculator to a low value, turning the calculator dial clockwise, pin 24 moves against arm 21 turning device 52 7e and, through arms 33 and 34, the :lever 62 chang ing the light scales from high to lowcalibration and removing the shunt resistance 53 from across the instrument armature. As this change occurs, arm 21 moves out of the path of movement of pin 24 and lets the pin pass by and arm 26 moves into such path to the left of such pin. Simultaneously the low light values on the calculator scale l'2 are brought adjacent the index l3. It is thus seen that the instrument calibration includ ing its sensitivity and scale values may be changed by adjustment of the calculator light scale through the lost-motion driving means described in a manner to assure that the correct instrument calibration will be used for accurate and convenient settings of the calculator. There is a relatively small but desirable overlapping range on the calculator'light scale that may be used with either instrument calibration. For instance, the light values from 40 to 50 may be brought into reading position with either instrument calibration. It is understood that the parts repre sented in Fig. are greatly expanded in an axial direction, and that the front-wall 29 of the casing in which part 32 is pivoted is not shown in this figure.

The instrument'pointer 6 swings between the front wall of the casing and the supporting plate 60 of the scale changing structure where it may beobserved through the window openings against the instrument scale in use as a background. The plates 60 and BI which support the scale changing mechanism and switch are riveted together in spaced relation and mounted on and secured to the front wall of the permanent magnet 40' by the same bolts 49 and 5|! that secure the magnet to the light sensitive cell structure. .The bolt holes for this purpose in plate 6| are indicated in Fig. 5 at 49c and 50a. The tab 44 which supports the core of the instrument is an integral extension of plate 6|. .The stationary switch contact 54a is mounted on a sheet of in sulation 6! (see Figs. 3 and 4) clamped between the right-hand pole of magnet 40 and plate 5|. When the front section of the instrument casing is removed and the two clips 40 are removed, the electrical measuring instrument together with the light sensitive cell scale changing unit and switch may be lifted out of the back section of the instrument as a unit.

The light meter is preferably provided with a releasable pointer stop which prevents movement of the pointer except when released. This prevents movement of the pivoted armature and hence relieves the pivots of some'wear and shock when the device is being carried about in a pocket or is not otherwisein use. It also permits the user to take a light measurement and preserve the reading as long as he wishes. This :pointer lock may comprise a light spring frame part 68 shown in Fig. 5 secured to the front of plate 60 by the lower studs 59 and extending around the window area with the crossbar'portion of such frame sprung away from the plate 60 to rest lightl against the under side of pointer 6 in any position of its deflection. The spring frame 68 may be flexed toward plate 60 and away from the pointer by a push rod 69 extending through the calculator plates I and and the top wall 29 of the casing and accessible from the front of the device. The push rod extends through the central opening in the calculator rings 2 and 3 and hence does not interfere with their operation. It is just outside the arc of swing of the outer end of thepointer 6 and hencedoes not interfere therewith. The rod 69 may be held in place by screw-threading its inner end into spring frame 68. Hence the spring frame itself normally holds the push rod as well as the crossbar of such frame in pointer locking position. When a light measurement is to be taken, the back window of the device is directed in the light measurement direction and the push rod 69 shoved in by the thumb or finger. This releases the pointer which then deflects to the proper measurement position after which the push rod 69 is released and the pointer becomes locked in the measurement position and may be read at leisure. Also this is of considerable convenience in that the position of the meter may be shifted between a light measurement and the reading of the measurement. In any case where the calculator is to be removed from the casing, the push rod 69 may be unscrewed'from spring frame 68 and pulled out to the front. If, then, the meter is to be used with the calculator removed, the push rod is again inserted through the opening provided therefor in the front wall of casing part 29 and screwed into the spring frame 68. In this case a somewhat shorter rod may be substituted if desired. The removal of the push rod for such assembly or disassembly operation is necessary only in case its outer end is provided with a knob larger than the openings through which the rod passes.

In accordance with the provisions of the patent statutes, I have described the principle of operation of my invention, together with the apparatus which I now considerto represent the best embodiment thereof, but I desire to have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States is:

In a toggle mechanism, supporting structure, a lever member pivotally suported on said supporting structure, a compression spring pivotally connected between said supporting structure and lever member to impart toggle action to the movement of said lever about its pivot, the point of connection between spring and lever lying between the point of connection of said spring to said supporting structure and the pivot point of said lever, said compression spring having one of its connecting ends doubled back toward its center so that the spring is substantially effectively longer than the distance between its points of connection between the supporting structure and lever arm.

ALLEN G. STIMSON.

REFERENCES CITED The following references are of record in the idle of this patent:

UNITED STATES PATENTS 

